# Full text of "Text Book Of Mechanical Engineering"

## See other formats

```i!

882

Appendix II.

by re-heaters, the only reason for whose success lies in the remark-
able economy of heat thus supplied, some six times as efficiently
as when used in a steam boiler.

P. 605-8. Plotting the Curve pVn = C,—The pressure
for given volume, or volume for given pressure, can be found by
using a table of logarithms, for

Note that   ~~1

common logs.   I

are used.    J

log/ -f fllogV — log C
log/ = logC - «logV

, .   ,r      JosjC-log/
and logV =     &         to/

n

The values / or V may then^be deduced, being the numbers
corresponding to their logarithms. Or, again, the values n and C
for a given curve, may be found by construction. Taking the
given expansion curve, Fig. 842, measure every pressure and

FMf.842.

— J -

volume at any points i, 2, 3, 4, 5, arid, on a new diagram, shewn
below, plot their logarithms, drawing the best straight line A B
through the plotting. Then

AC

C"B

and log/ 4- — logV = logC

C B

Putting in the values for log/ and log V, taken anywhere, log C```